You can either change the Activity for the route to Direct, or create additional direct routes for the portions of the trip that are not on a road.

Wouldn't it be nice if Garmin had foreseen this very common issue, and allowed for user selected additional routing options within a single route, following roads where available, and using a user selected option for off road calculations, all within the same route?

So once I change the activity in basecamp from Motorcycle to Direct do I just drag those purple way points in the box where I've been adding each wp? I'm scared to do something that will wipe out all the work I'm doing for this track. I'm still learning how to do this stuff.